Fuel cells are devices that can convert chemical energy directly into electrical energy through electrode reaction of hydrogen and oxygen. A fuel cell typically includes multiple fuel cell units. Each fuel cell unit includes two electrodes (anode and cathode) separated from each other by an electrolyte component. The fuel cell units are stacked to be electrically in series to form a fuel cell stack. An electrochemical reaction occurs as appropriate reactants are supplied to each electrode, i.e., fuel is supplied to one electrode and oxidant is supplied to the other electrode, thereby creating an electrical potential difference between the two electrodes. As a result, electrical energy is generated.
In order to supply reactants to each electrode, a particular interfacial component, often referred as “bipolar plate” that is placed on two sides of each individual cell, is used. The bipolar plate is usually in the form of a single component as the supporting body disposed in the vicinity of the anode or cathode. The bipolar plate is a key component of the fuel cell stack. During operation the fuel cell stack, the bipolar plate performs the following functions to ensure an optimal working condition and a long stack lifetime: (1) acting as an electrical conductor between adjacent cells (a cathode and an anode formed on the opposite sides of the bipolar plate electrically connect the single cell in series to form a fuel cell stack); (2) supplying reactant gases (transfer media) to the electrodes through flow channels; (3) facilitating water and heat management and preventing leakage of coolant and reactant gases; and (4) providing structural support for membrane electrode assembly (MEA).
Graphite plates, metal plates and composite plates are the most commonly used bipolar plates. The common problems associated with all these bipolar plates include complex manufacturing process, high cost, and high weight.
A pair of bipolar plates generally sandwich a MEA to form a fuel cell unit, and a fuel cell stack is formed by stacking multiple fuel cell units in series. Thus, the electrical current output of the fuel cell stack is in the series form, i.e., the total voltage V=V1+V2+Vn. As a result, when one of the fuel cell units in the stack is damaged, the voltage output of the entire stack will be affected.